Amplifying Voices Webinars

Amplifying Voices Webinar Series

The ASLO Early Career Subcommittee is pleased to invite you to our webinar series, “Amplifying Voices: Early Career Researchers Making Waves in Aquatic Sciences.” This webinar series promotes the exciting work of early career aquatic scientists from underrepresented groups in our global community. The series features presentations from early-career researchers. In each session, the presenters share their work in 20-minute presentations followed by a moderated Q+A. The presentations are free to the public.

Webinars are presented each month and are recorded. The videos are uploaded to ASLO's YouTube channel and are freely available for viewing.

November 11, 2021
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Brittni Bertolet
University of California, Irvine (USA)
Does microbial diversity really matter? Evidence from sediment methane production

Presentation Abstract

Advances in our understanding of the diversity of lake sediment microbial communities has uncovered numerous questions about how microbial processes influence large-scale ecosystem function. In lake sediments, microbial communities play a critical role in mediating carbon diagenesis and fate, but it is still uncertain how differences in community composition and structure influence function (carbon dioxide and methane production) independent of differences in the environment. We used both comparative and experimental approaches to 1) identify drivers of sediment microbial community structure and function and 2) develop mechanistic understanding of how variation in microbial communities influence ecosystem responses to environmental change. We find that pH is an important environmental determinant of sediment microbial community composition across space and that, in an experimental context, pH acts as an environmental filter on community assembly. Further, we find that variation in community composition influences sediment function irrespective of the pH environment. Evidence for the pH-independent role of microbial community composition in ecosystem function has substantial implications for understanding environmental change. We provide robust evidence that lakes with sediment microbial communities indicative of near-neutral pH are expected to respond stronger to increases in organic matter supply (eutrophication) than lakes with communities indicative of low pH conditions. As the eutrophication of lakes increases in the 21st century, understanding how variation in microbial processes contribute to ecosystem responses will be key to developing mechanistic understanding and prediction of change.

Patricia Valdespino-Castillo
Lawrence Berkeley National Laboratory (USA)
Synchrotron infrared studies of biomineral microenvironments

Presentation Abstract

Biomineral formation is a key process to understand the linkage between biological activity and sedimentary structures in the biosphere. The fossil record holds evidence that microbial systems have mediated the precipitation of carbonates as early as ∼ 3,500 Ma ago, and still today they are key participants in the formation of massive carbonate constructions in natural waters. Microscale has been a relevant challenge to understand biomineral formation. This research questions have been invigorated recently by using advanced imaging technologies, such as Synchrotron based-Fourier Transform Infrared spectromicroscopy (SR-FTIRs). This is a non-labelled, non-destructive, spatially resolved strategy that allows chemical characterizations of live cells with microscale resolution. SR-FTIRs analyses revealed structural and functional features of microbial-only biomineral forming systems (microbialites) but also of host-microbiota systems (coralline algae). These results are based on spatial correlations of biomolecules and mineral infrared signals in the extracellular polymeric substances (EPS) matrix. These first results provide insight into the characteristics of the microsites of mineral formation, and are useful to inspire bio-cement development and carbon sequestration technologies in an increasing CO2 world.

December 9, 2021
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Aasif Mohmad Lone
Indian Institute of Science Education and Research (India)
The late Holocene lacustrine proxy records from Northwest Himalaya: Implications to regional hydroclimate variability

Presentation Abstract

The Northwest Himalaya (NWH) is idealistically located at the intercept between the mid-latitude westerlies (WD) and the Indian Summer Monsoon (ISM). The interplay between these two major precipitation drivers over the NWH have been best understood from the lacustrine sedimentary proxy records. Considerable efforts have been directed towards developing past monsoonal records from Himalayan region to improve our understanding of the Himalayan Climate System (HCS). Previous records have shown that small changes in the climate, including shifts in the regional precipitation and temperature patterns will have large consequences on the landscapes, Himalayan Rivers, glaciers and the regional livelihood as monsoonal precipitation is vital for sustaining the regional water stocks and supporting agriculture and rapidly growing economy. In the present research work, we seek to understand the trends, variability and possible driving mechanisms in paleoclimate variability using multiproxy records from lacustrine geoarchives of Kashmir Valley (NWH) to better understand the regional hydroclimate system. Several of these past climate records reveal near synchronous variability (within dating uncertainties) with other regional moisture conditions and global climatic events. The results highlight the importance of studying multiproxy records from Himalayan lacustrine archives to infer past hydroclimate variations and constrain the driving forces modulating the Himalayan climate system.

Bhakti Salgaonkar
Department of Microbiology, Goa University (India)
Bioprospecting of Halophilic Archaea from the Food Grade Iodised Crystal Salt from a Saltern of India

Presentation Abstract

Haloarchaea are polyextremophile microorganisms belonging to the domain Archaea which are able to endure and proliferate in extreme physical parameters such as radiations (UV), temperature, pressure and geochemical parameters such as pH, salinity, redox potential, etc. The ability of haloarchaea to thrive in extremes demonstrates their great prospective for biotechnological processes in harsh industrial conditions. Culturable halophilic archaeal diversity of iodised crystal salt obtained from the solar salterns of Vedaranyam, Tamil Nadu, India was explored by surface spreading the salt crystals and incubating the plates for 30-45 days resulted in the growth of bright pink-orange-red pigmented colonies. The cultures were purified and identified using polyphasic approach. Halophilic archaeal produce various shades of bright orange-red C50 carotenoids such as the α-bacterioruberin (BR) which protects the cells from the harmful UV radiations, which in turn can be exploited in sunscreens. Haloarchaea are reservoir for novel enzymes known as “Extremozymes” because of their catalytic activity at extremes of environmental conditions, therefore serve as powerful tool in industrial processes operating at extreme conditions. Haloarchaea are known to synthesize biodegradable plastics known as polyhydroxyalkanoates (PHAs) which are biocompatible and therrfore finds applications in biomedical engineering. Further, haloarchaea secrete broad-spectrum growth inhibitory substances known as “archaeocins/halocins” which can be employed in leather industry and in food industry as preservatives. Haloarchaeal isolates are known for intracellular sequestration of heavy metals and are potential candidates for bioremediation of metal contaminated hypersaline environments.

January 27, 2022
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Speakers:

Justyna Hampel
Department of Ecology, Environment and Plant Sciences, Stockholm University, Sweden

Microbial communities respond predictably to built habitats on the seafloor

Presentation Abstract

Ocean seafloor is a complex ecosystem where habitat heterogeneity is one of the major factors influencing biodiversity. Widespread natural, geological features like hydrothermal vents and seeps create unique environments and select for unique populations of micro and macrofauna. In contrast, artificial habitats are understudied but might play equally substantial role in shaping biodiversity, community composition, and ecosystem function. Built habitats on the seafloor are increasing as the consequence of ocean sprawl however, they pose unknown effects on benthic communities. This study addresses the impact of model built environment, shipwrecks, on microbial diversity and microbiome structure in surrounding sediment. We report elevated microbial diversity and unique but uniform core microbiome in sediments around shipwrecks. We show that the ‘sphere of influence’ of these built habitats extends up to 200-300 m onto the seafloor. Supervised learning techniques made strong predictions of proximity to the structure based on archaeal and bacterial ASV. Notably, response of archaeal communities to built features was more pronounced than in bacteria. Core microbiome of archaea surrounding the shipwrecks was enriched in distinct communities not present at further distances. The strongest predictions of proximity to shipwrecks were in closest (2-9m) and furthest (1000 m) distance groups. We show that built habitats, although much younger than natural features, have similar effects on microbial diversity and community structure in marine deep biosphere and shape the microbiome in a predictable way. These findings are critical in learning how built habitats affect microbial communities in the global ocean in the Anthropocene.

Kuo Hong Wong (Josh)
College of Science and Engineering, Kanazawa University, Japan

Origin of the zinc-silicate decoupling in the subarctic Pacific

Presentation Abstract

Dissolved zinc (dZn) and silicate (Si) have similar distribution profiles in the global ocean. This coupling of distribution is baffling because the remineralization of Zn and silicate occurs at different timescales, with Zn regenerated at shallower depths than Si. In the Southern Ocean, however, strong vertical mixing of water masses homogenizes the distributions of dZn and Si, which are then transported to the other ocean basins via the ocean conveyor belt. An exception is the subarctic Pacific, where dZn and Si decouple. To investigate this anomaly, we determined the dZn and Si distributions in the subarctic Pacific (GEOTRACES GP02 line), Gulf of Alaska, and the western Bering Sea. These regions are high nutrient low chlorophyll regions with very low surface dissolved iron (dFe) concentrations (< 0.1 nM). Our data reveal increased uptake of dZn by phytoplankton in coastal regions where supplies of dFe from terrestrial sources alleviate Fe limitation. Hence, the resulting sinking particles have high Zn content. Subsequent remineralization releases Zn at shallower depths than Si but unlike in the Southern Ocean, the absence of vertical mixing processes prevents the homogenization of dZn and Si. Strong advective fluxes from the coastal regions to the subarctic Pacific transport intermediate water with a high dZn/Si ratio and cause distortion to the globally homogenous dZn and Si distribution. dZn/Si ratio decreases away from the coastal regions as water mass mixing weakens this anomaly. This propagation pattern is consistent with that of dissolved manganese, which is used to trace water mass originating from coastal regions.

February 24, 2022
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Speakers:

Arkaprava Mandal
Indian Institute of Science Education and Research Kolkata, India

Tracking the ecological health of a coastal ecosystem from the North-East Bay of Bengal- Applicability of benthic foraminifera as bioproxy

Presentation Abstract

Since the beginning of the industrial revolution in the mid-18th century, climate change has become a topic of increasing concern. The present study has been done in marginal environment of Junput, West Bengal, India adjacent to the northeast Bay of Bengal. This study site was once part of mangrove vegetation, but now hardly mangrove left. The site shelter quite a few endangered species like the horseshoe crab, olive ridley turtle, and fiddler crab, but now this area has degenerated into the densely populated coastal zone and become a reputed fishing zone. In order to learn the present stressed condition of the studied area and predict how these stresses might evolve in the near future, it requires testate marine organisms like benthic foraminifera. Benthic foraminifera are well preserved in the sediments and sensitive to changes in environmental conditions. The present study investigates the applicability of this group to track the climatic change in the study area. The study encompasses a number of sampling points from intertidal area representing hydrodynamic gradients within the freshwater-influenced ecosystem. The present study reveals benthic foraminifera diversity and abundance were overall low, and the assemblage dominated by calcareous species. The calcareous species Ammonia spp., Asterorotalia trispinosa, Quinqueloculina sp., Globigerinoides sp., and agglutinated species Trochammina inflata were observed. The presence of only three calcareous taxa and almost absence of agglutinated taxa indicate the degradation of ecological quality of the coastal Bay of Bengal. Apart from optimally preserved tests, many broken tests were observed. The broken tests were probably the result of mechanical damage or indicating the taphonomic alteration in intertidal sediment. The dominance of populations of Ammonia spp. across studied sites indicating shreds of evidence of increasing anthropogenic stress. However, the generated data set can be compared to similar marginal marine environments globally to developing an environmental proxy for future tracking of the prevailing environmental conditions of the coastal environment.

Chakresh Kumar
Indian Institute of Science Education and Research Kolkata, India

Seasonal dynamicity of environmental variables and water quality index in the lower stretch of the River Ganga

Presentation Abstract

Rapid increase in industrialization and urbanization has resulted in unbalanced release of sewage and pollutants into the River Ganga. Unrestricted and unchecked discharge of both municipal and industrial waste has resulted in considerable deterioration of water quality along the entire course of the river and specifically along the lower stretch that flows through the state of West Bengal before opening into the Bay of Bengal. The lower stretch, also referred to as Bhagirathi-Hooghly records much higher coliform count and dissolved nutrients which renders the surface water unfit for usage. Sites including the heavily populated suburban sites of Kalyani, Tribeni, Halisahar, Naihati, Chandannagar, Palta, Barrackpore,Dakshineswar and Kolkata were monitored seasonally to understand the rapidly changing water quality. Samples were classified into point sources (PS)- areas of direct discharge of municipal wastes and surface water (SW)- areas away from the direct influence of the point source. Water samples were collected from PS and SW over pre-monsoon (March-June), monsoon (July- October) and post-monsoon (November- February) seasons of 2019. In-situ environmental parameters including surface water temperature, dissolved oxygen, pH, salinity, total dissolved solids (TDS) and electrical conductivity (EC) were measured in triplicates during time of sampling. Both pH and DO were found to be strongly influenced by seasonal precipitation and in turn affected the water quality. Dissolved nutrients including nitrate and o-phosphate concentration showed significant seasonal variation. Relatively higher concentration of dissolved nutrients in the PS stations compared to the SW stations indicated the possible release of municipal and industrial waste directly into the river. Increase in nutrient concentration in turn strongly influenced environmental parameters including pH, DO and EC. Variations in these four parameters, including pH, DO, EC and dissolved nitrate indicated very bad water quality along most sampled sites. Water quality index provided comprehensive insights into the condition of the surface water. Along with a strong seasonal influence, WQI indicated that surface water from most of the sampled stations were unfit for usage.

Special Session, March 17, 2022
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Speakers:

Leslie Townsell
ASLO DEIJ Intern

An Introduction and Tour of the ASLO Diversity, Equity, Inclusion, and Justice Forum

Anwesha Ghosh
ASLO Early Career Committee Member

Putting things into perspective - a story of the changing face of the Indian Sundarbans

March 31, 2022
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Speakers:

Ahmed Mohammed Nazem Elsayed Elreedy
Institute of Technical Microbiology, Hamburg University of Technology, Germany

Innovations in bio-electrochemical systems as a powerful "waste-to-energy" tool

Presentation Abstract

Anaerobic biological treatment of saline phenolic wastewater has some limitations such as slow adaptation, low biodegradability, and salinity-derived washout of biomass, though this technology has some benefits in terms of bioenergy recovery, simplicity in operation, and economic rationality. Therefore, we propose a packed-bed circular baffled reactor (PB-CBR) along with a co-metabolism strategy for phenol adaptation at a salinity level of 10 g-NaCl/L. Phenol and glucose were gradually increased and decreased to 0.9 and 1.0 g/L, respectively. Stable and efficient performance was achieved with > 99.9% phenol removal, ~98% overall biodegradability, and ~ 0.3 L CH4/gCOD. A sudden increase in phenol to 2 g/L was then examined, where phenol removal dropped to ~ 19% after 30 d; after another 30 d, the removal was negligible even when phenol was decreased to 1.7 g/L. The compartment-wise analysis of PB-CBR showed that phases-separation, along with all compartments, maintained the overall efficiency, particularly when facing salinity or phenol shocks; otherwise, earlier compartments achieve ~ 95% of efficiency. The microbial community analysis showed that Corynebacteriaceae, Syntrophaceae, Kosmotogaceae, and Synergistaceae were key players in phenol-degradation. Using readily biodegradable co-substrate enhanced biodiversity. Eventually, and according to a cost-benefit analysis, the present work offers a promising opportunity to treat phenol-based saline effluents in an efficient, sustainable, and affordable way.

Fousiya Aa
Department of Earth Sciences, Indian Institute of Technology, Kanpur, India

Marine calcifiers as timekeepers: Monsoonal variability and ocean surface temperature reconstruction

Presentation Abstract

Marine calcifiers are the most important components of the marine ecosystem that grow in the Tropical Oceans. They are widely known as the best archives to provide high-resolution records of ocean atmospheric variabilities on sub seasonal resolution spanning up to a few hundred years. Signatures preserved in these organisms are known to provide useful information and reconstruction of Sea Surface Temperature (SST), Sea Surface Salinity (SSS), upwelling intensity, oceanic circulation etc1. Lakshadweep Islands in the north Indian Ocean harbour various types of such calcifiers and various workers have recently studied them for paleoclimatic/paleo-environmental reconstruction. However, the atmospheric CO2 rise during the post-industrial era has resulted in a decrease of ~0.1 unit in surface ocean pH, a process commonly known as Ocean Acidification (OA)2, which has highly threatened the growth and existence of these marine calcifiers . In this talk, I will shed light on the significance and resilience of Corals and Giant Clam shells (two important marine calcifiers) growing under large variability in physical and biological processes in a strongly upwelling region of the Tropical Indian Ocean. Our preliminary records reveal that even short high temperature events could significantly perturb the biology of marine calcifiers and require long recovery phases. These results are particularly significant for conservation efforts of some of the most endangered marine calcifiers growing in regions in with on-going global warming trends.

April 28, 2022
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Speakers:

Radhika Bhargava
Department of Geography, National University of Singapore

Previous shoreline dynamics determine future susceptibility to cyclone impact

Presentation Abstract

Extreme weather events are a cause of mangrove forest loss and degradation globally. Almost half of the world’s mangroves are found in the tropical cyclone belt, and forests often experience disturbance in structure, functioning and ecosystem service provision. Understanding the factors that increase the vulnerability of mangroves to such disturbances is a challenge. Using a novel remote sensing analysis combining water class change with vegetation classification, we showed that mangrove loss across multiple cyclone events is influenced by previous erosion history, suggesting that the prior state of the coastline affects susceptibility to future disturbance events. During Cyclone Amphan in May 2020, more than 1200 km2 of mangroves were damaged and 40.6 km2 of shoreline was lost. Cyclone Amphan caused the most damage out of 3 recent cyclones, with the most mangrove loss (18.8%) experienced along shorelines that were eroding over the past 35 years. This can be explained by the long-term effect of erosion on the overall intertidal morphology of the shoreline. Landscape-scale mangrove management, particular of sediment budgets is essential in order to switch previously eroding mangroves to a state where they can withstand cumulative storm impacts.

Saumya Silori
Biological Oceanography Division, CSIR-National Institute of Oceanography (India)

Contrasting phytoplankton and biogeochemical functioning in the eastern Arabian Sea shelf waters recorded by carbon isotopes

Presentation Abstract

This study examines the relationship between the isotopic signature of phytoplankton-derived particulate organic matter (POM) (δ13CPOC) and estimates of growth rate and community composition along a north-south gradient in the western Indian shelf waters which possess contrasting biogeochemistry and mixed layers depths. The Eastern Arabian Sea/western Indian shelf turns highly productive due to the SW monsoon-induced upwelling at its southern region and experiences drastic seasonal reversal. We have characterized the POM pool by quantifying Chla, particulate organic carbon (POC), and particulate nitrogen (PN), C:N ratios, along with δ13CPOC values during the SW Monsoon. The prevailing physicochemical features contrasted between the southern (8◦N to 12◦N) and northern (13◦N to 21◦N) stations. Close couplings between POC, PN, and Chla contents indicated the autochthonous nature of POM. Low temperature, shallow mixed layer depths (MLDs), high concentrations of nutrients, POM, and Chla, marked the upwelling signature in the south. Conversely, relatively higher temperatures, salinity, deeper mixed layers (MLs), lower concentrations of nutrients, POM, and Chla were evident at the northern stations. Five times higher POC concentrations were noticed in the south (65.5 ± 22.0 μmol L−1) than in the north (12.8± 5.4 μmol L−1) within the MLs. Phytoplankton community shift (based on marker pigment analysis) and the δ13CPOC values were closely coupled. The nutrient replete microphytoplankton (diatoms) dominated southern stations were associated with higher values of δ13CPOC (−23.0 ± 2.3‰) which was attributed to faster growth rate; conversely, the oligotrophic nitrogen-limited waters in the north dominated by pico and nanophytoplankton (haptophytes and cyanobacteria), were characterized by distinctly lower δ13CPOC values (−26.6 ± 0.9‰). Phytoplankton growth rates based on a model were consistent with this trend. Our results show that the autochthonous POC is the primary source of organic matter, and the contrasted biogeochemistry-induced phytoplankton communities and their growth rates mostly governed the δ13CPOC variability in this region. However, the lower values in the subsurface waters at the south were likely to be influenced by light limitation and heterotrophy.

May 26, 2022
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Speakers:

Nirupama Saini
Indian Institute of Science Education and Research Kolkata

Investigating the seasonal abundance and distribution pattern of microplastics in a Mangrove ecosystem of northeastern coastal Bay of Bengal

Presentation Abstract

Other than the bigger pieces of the plastics, the plastic pieces of size smaller than 5mm, also termed as microplastics, are being recognized as one of the global problems. This study aims to investigate the abundance and composition of microplastics in surface water of the westernmost part of Sundarbans, during monsoon and post-monsoon seasons to better understand the seasonal variations and determine the source of microplastic pollution and its migration features. The world's largest contiguous mangrove forest, Sundarbans, is a UNESCO world heritage site and a Ramsar site. Sundarbans is shared between Bangladesh and India, which are among the top mismanaged plastic waste generating nations and are discharging plastic waste downstream through rivers and coasts, making the Sundarbans a cesspit for plastic waste. Moreover, this mangrove ecosystem is formed by the super confluence of the Ganga, Brahmaputra, and Meghna rivers. These rivers are among the top ten plastic waste carriers and combined flow of them can discharge up to 3 billion pieces of microplastics per day into the Bay of Bengal. The microplastic abundance varied from 3items/liter to 66 items/liter with a mean abundance of 22.27±11.8 in monsoon; from 3items/liter to 34items/litre with a mean abundance of 14.52±7.97 in post-monsoon. Overall, fibers were predominant and constituted around 58 percent of total microplastics. Based on color, colorless and white microplastics are more in number. Spectroscopic analysis revealed polypropylene as the most abundant type of polymer. The study provides the preliminary knowledge regarding the microplastic pollution in Sundarbans which can be further utilized in understanding its long-term implications on the ecosystem.

June 30, 2022
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Speakers:

Richard Mugani
PhD Student
Cadi Ayyad University, Faculty of Sciences Semlalia, Marrakech, Morocco

Impact of microcystins on the dynamics of the rhizosphere microbiota: a focus on extra- and intracellular microbial enzymatic activities

Presentation Abstract

Cyanobacterial blooms have become a global threat due to toxins released into water bodies. These cyanobacteria-contaminated waters are used in agriculture without treatment. Nevertheless, effects of these cyanotoxins on aquatic and soil microbiota are not fully understood. This study investigates how these cyanotoxins affect the microbial activity of water and soil by measuring the microbial activities of key enzymes involved in biogeochemical cycles. Four enzymes were analyzed by the fluorometric method using MUB- linked substrates: arylsulfatase (ARS), β-glucosidase, N-acetylglucosaminidase (NAGase), phosphatase, and three others were quantified by colorimetry: dehydrogenases, proteases, and urease. Three Bacterial strains previously isolated in bloom colonies, water, and soil highly contaminated with cyanotoxins were inoculated into 48 soil pots, from which 24 soil had been sterilized and 24 not sterilized. These pots, placed in the greenhouse, contained pea plants in 5 replicates and were irrigated for three months with 0, 50, and 100 µg/L MC-LR. Finally, the soils were collected, and the soil's enzymatic activities and chemical properties were analyzed, including loss on ignition (LOI), total phosphorus, and carbon/nitrogen/sulfur analysis by combustion (NCS). The results obtained showed a significant difference in the decrease of all enzymatic activities when irrigating with high MC-LR concentration. Bacterial inoculation showed increased enzyme activities when triple bacterial inoculation was applied. Similarly, there was a positive correlation between bacterial inoculation and total phosphorus concentration and NCS. Our results indicate that MC -LR diminishes soil microbial activities. However, inoculation of soil with cyanotoxin-tolerant bacteria seems to counteract the adverse effects of these pollutants.

Archana Tiwari
Diatom Research Laboratory, Amity Institute of Biotechnology, Amity University, Noida, India

Role of Diatom Algae in carbon dioxide mitigation and generation of high value products

Presentation Abstract

The increasing impact of climatic change has severely influenced all the living organism on earth. Algae are among the opaquest photosynthetic microorganism found in oceans, rivers, and freshwaters and they play a major role in reducing global warming as they fix more than 25% of atmospheric carbon-dioxide. They are a reservoir of untapped potential with the multifaceted application including carbon-dioxide mitigation, vital role in the aquatic food web as primary producers, wastewater remediation by quenching pollutants originating from diverse sources like industries, agricultural and human sources. Despite their abundance and diversity in nature, few species are currently used for biotechnologically applications. Diatom Biorefinery has gained importance in recent years as more and more algae are identified and explored as a source for lipids, pigments, and other biomolecules. The diatom biorefinery involves exploiting the diverse roles of diatoms in carbon-dioxide mitigation and generation of high amount of lipids with EPA and DHA, fucoxanthin, and other active molecules with immense potential as new-age drug molecules and providing sustainable solutions towards a circular economy.

July 28, 2022
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Speakers:

Dr. Prasun Goswami
National Institute of Ocean Technology (NIOT), Atal Centre for Ocean Science and Technology for Islands, Ministry of Earth Sciences, Govt. of India

Plastic pollution and beyond: do microbes hold the key towards a sustainable solution to this global crisis?

Presentation Abstract

Plastic is a wonder product, though, significant concerns arise about plastic leakage to the environment. Tiny plastic particles, so-called microplastics (MP), have been detected ubiquitously. They are bioavailable for many organisms and may cause negative effects. The present study was conducted at first to understand the nature, behavior, and interactions of microplastics in the marine environment. We compared microplastic levels in the Andaman Sea and the Arabian Sea and found, that MP levels at the Arabian Sea were significantly higher than in the Andaman Sea. Further, to understand food web MP interaction, we analyzed MP ingestion rates in marine zooplankton communities. Clear evidence of a high amount of MP ingestion was observed in zooplankton. Food chain transfer of MPs in some commercially important carnivorous fishes was also noticed. Polyethylene and polypropylene are the most common polymer types detected. These MP polymers get quickly colonized by a wide range of microorganisms, through biofilm development, which is known as the "plastisphere." The plastic degradation potential of these ‘plastisphere’ associated microbes was assessed. Based on our preliminary screening we prepared a bacterial consortium using four highly potential LDPE utilizing bacteria and incubated with LDPE for 120 days. After 120 days on average, nearly 47% LDPE degradation was observed. These results suggest that the bacterial consortia used in this work have great potential to degrade plastics and solve the problem. However, further research is required to develop innovative, cutting-edge, and eco-friendly technology to solve plastic pollution.

Ms. Diksha Sharma
CSIR-National Institute of Oceanography, Biological Oceanography Division, India

Impacts of Zn and Cu enrichment under ocean acidification scenario on a phytoplankton community from tropical upwelling system (Arabian Sea)

Presentation Abstract

Increasing dissolution of CO2 in the surface ocean is rapidly decreasing its pH and changing carbon chemistry which is further affecting marine biota in several ways. Phytoplankton response studies under the combination of elevated CO2 and trace metals are rare. We have conducted two consecutive onboard incubation experiments (R. V. Sindhu Sadhana; August 2017) in the eastern Arabian Sea (SW coast of India) during an upwelling event. A nutrient enriched diatom bloom was initiated onboard and grown under ambient (approx. 400 μatm, A-CO2) and high CO2 levels (approx. 1000 μatm; H–CO2) with different zinc (Zn; 1 nM) and copper (Cu) concentrations (1 nM, 2 nM and 8 nM). Phytoplankton community composition and the dominant genera were different during these two experiments. CO2 enrichment alone did not show any significant growth stimulating impact on the experimental community except enhanced cell density in the first experiment. Addition of Zn at A-CO2 level revealed no noticeable responses; whereas, the same treatment under H–CO2 level significantly reduced cell number. Considerably high protein content under H–CO2þZn treatment was possibly counteracting Zn toxicity which also caused slower growth rate. Cu addition did not show any noticeable impact on growth and biomass production except increased protein content as well as decreased carbohydrate: protein ratio. This can be attributed to relatively higher protein synthesis than carbohydrate to alleviate oxidative stress generated by Cu. The centric diatom Chaetoceros and toxin producing pennate diatom Pseudo nitzschia showed no significant response to either CO2 or Zn enrichment. Large centric diatom Leptocylindrus and Skeletonema responded positively to Zn addition in both CO2 levels. The former species showed the most sensitive response at the highest Cu and H–CO2 treatment; whereas, the pennate diatoms Nitzschia and Pseudo-nitzschia (toxigenic diatom) showed higher resilience under elevated CO2 and Cu levels. This observation indicated that in future ocean, increasing CO2 concentrations and trace metal pollution may potentially alter phytoplankton community structure and may facilitate toxigenic diatom bloom in the coastal waters.

August 25, 2022

Speakers:

Shailesh S. Nair
Postdoctoral Researcher
Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Science

Decoding the mechanisms behind the recurrent mutualism between marine Synechococcus sp. PCC7002 and heterotrophic bacterial community despite environmental interference under long-term coexistence

Presentation Abstract

Marine algae are rightly called the “lungs of the sea”. They produce approximately 70 % of the oxygen that sustains life on earth and regulates the marine primary productivity on which the whole marine life is sustained. Among these algae, picocyanobacteria (mainly Prochlorococcus and Synechococcus) are the most abundant group, contributing up to 60% of the carbon fixation in the oceans and 30% of the global primary production. On the other hand, marine heterotrophic bacteria convert the organic matter derived from marine life (including algae) into inorganic nutrients. These inorganic nutrients in turn support the growth of marine algae. However, most of the open ocean is poor in these nutrients. Despite, this Prochlorococcus and Synechococcus can thrive in such nutrient-poor regions. In this work, we show that Synechococcus and associated heterotrophic bacterial communities tend to move towards mutualistic relationships on long-term coexistence by undergoing bacterial community succession. Once the mutualistic relationship is established, the bacterial generation of essential nutrients (especially nitrogen) supports the long-term, healthy growth of Synechococcus. Furthermore, we show that environmental factors such as the provision of external nutrients disrupts their established mutualism. However, once the effect of external environmental influence is weakened, they re-established the disrupted mutualism under long-term coexistence. Using modern methodologies such as metagenomics, metatranscriptomics and 15N isotopic nitrogen fixation analysis, we reveal that the associated bacterial nitrogen fixation triggered the re-establishment of mutualism. During this process, bacterial community structure and functions underwent tremendous adjustments to achieve the driving effect, and a co-generation of nitrogen, phosphorus, iron and vitamin by the heterotrophic bacteria sustained Synechococcus’s prolonged healthy growth. Our findings suggest that Synechococcus and heterotrophic bacteria may have an inherent tendency towards mutualism despite environmental interference. This may exhibit their co-evolutionary adaptations in nutrient-deficient environments.

Caroline Ganglo
PhD Candidate
University of Koblenz-landau Systemlink

Chironomids reduction alters carbon dynamics in ponds

Presentation Abstract

Shallow lentic aquatic ecosystems are important repositories of organic carbon and hotspots of carbon cycling and greenhouse gas emissions. Tube-dwelling invertebrates, such as chironomids, can be key players in C processing in these water bodies, yet their effect on C cycling at ecosystem scale are largely unknown. We tested whether a 41% reduction in chironomid abundance and a shift in benthos community, found after application of the biocide Bacillus thuringiensis israelensis (Bti), have implications for C fluxes, pools, and organic matter decomposition. Data were collected over one year in shallow and deep habitats of 12 experimental floodplain pond mesocosms (FPMs), half of them treated with Bti. C fluxes were measured as CO2 and CH4 evasion, and as emerging merolimnic insects. C pools were measured as dissolved inorganic and organic C in surface and pore water, as well as organic C in sediment, plants and macroinvertebrates. We further estimated organic matter decomposition from tea bag incubations. The fluxes, pools and decomposition rates varied seasonally and differed systematically between different habitats of the ponds. In ponds treated with Bti, for which an increase of CH4 evasion has been reported, we found lower concentrations of dissolved organic C in surface water, while all remaining pools, fluxes, and rates were unaffected. These results suggest a rather partial influence of changes in macroinvertebrate communities caused by Bti application on C cycling in FPMs ecosystems, yet they confirm the existence of long-lasting effects on selected components of C budgets.

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